In ion implantation systems, an ion beam is directed towards a work piece (e.g., a semiconductor wafer, or a display panel) to implant ions into a lattice thereof. Once embedded into the lattice of the workpiece, the implanted ions change the physical and/or chemical properties of the implanted workpiece regions, relative to un-implanted regions. Because of this, ion implantation can be used in semiconductor device fabrication, metal finishing, and various applications in materials science research.
During a typical implantation process, the ion beam has a cross-sectional area that is significantly smaller than the surface area of a workpiece to be implanted. Because of this, typical ion beams are scanned over the surface of the workpiece to achieve a specified doping profile in the workpiece. For example, FIG. 1A shows an end view of a conventional ion implantation system 100 where an ion beam 102 traces over a scan path 104 to implant ions into the lattice of a workpiece 106. During this tracing, the ion beam 102 is often scanned over a first axis 108 (e.g., electrically or magnetically scanned) while the workpiece 106 is mechanically translated over a second axis 110. However, the beam could also be electrically or magnetically scanned over both the first and second axes 108, 110 in other embodiments.
Unfortunately, however, as the ion beam 102 traces over the scan path 104, the shape and/or cross-sectional area of the beam can vary somewhat, such as shown in FIGS. 1B-1F. For example, FIGS. 1B-1F show that as the beam 102 scans across the workpiece 106, the width of the beam can be larger near the center of the workpiece (central width Wc in FIG. 1D) and smaller near the edges (e.g., left and right widths, WL1, WR1 as shown in FIGS. 1B, 1F, respectively). If these variations in beam width are not accurately measured and accounted for, the doping profile actually formed in the workpiece 106 can differ from the specified doping profile. Such differences can result in the implanted workpiece not functioning as specified.
In order to help ensure that the ions actually implanted into a workpiece are commensurate with a desired dosing profile, ion implanters often include a beam profiler. A beam profiler measures the flux or current of the ion beam at different regions on the scan path 104, and assembles these values to generate a beam profile. Although conventional beam profilers are known, conventional beam profilers require substantial mechanical assemblies and/or complex signal processing. Therefore, aspects of the present disclosure relate to improved beam profiling techniques.